Microcrystalline Silicon Thin Films Deposited By ICP Assistant Magnetron Sputtering

Hydrogenated microcrystalline silicon (μc-Si:H) thin film is a competitive material in planar display area and solar cell industry. As a channel layer in the thin film transitor (TFT) and intrinsic layer in solar cell,μc-Si:H works with more efficient electron mobility and higher photovoltaic stability. Now in industry the most popular way to depositμc-Si:H thin films is based on chemical vapor deposition (CVD), such as hot filament chemical vapor deposition (HWCVD) and plasma enhanced chemical vapor deposition (PECVD). During HWCVD and PECVD process for the growth ofμc-Si:H, it often uses toxic and explosive silane as its precursor gas, which results in high cost in the security systems and gas recycling systems.Magnetron sputtering with simple equipment structure, easy scalability and high safty is a promising technique for the deposition ofμc-Si:H thin films. However, most sputtering sources often exhibit low ionization which results in poor crystallinity of silicon thin films deposited by magtron sputtering. To solve this issue, we developed a plasma source assistant magnetron sputtering system which employed inductively coupled plasma as plasma source for the growth of highly crystallized silicon thin films. In this thesis, we introduced exact deposition process and material characteristics ofμc-Si:H thin films by inductively coupled plasma source assistant magnetron sputtering (ICP-MS) system.In Section One, we introduced the state of the art of silicon thin film applications in planar display and solar cell industries. We illustrated different techniques for synthesis ofμc-Si:H thin films and summaried their characteristics. In the end of this section, we introduced the background of our project and pointed out the advantage of our system.In Section Two, we presented in detail our ICP-MS system. We demonstrated the plasma diagnosis by Langmuir probe and discussed the characteristics of our plasma source. In this section we also introduced the methods we employed for the analysis of silicon thin films.In Section Three, we studied the effects of H2 on the growth ofμc-Si:H thin films. First we fixed the total gas pressure and increased the hydrogen dilution ratio ([H2]/[H2+Ar]) gradually from pure Ar gas to hydrogen dilution ratio of 80%. We observed the effects of hydorgen dilution ratio on the properities of deposited Si films including microstructure, Si-H bonding configurations and optical band gap. And then we mapped crystalline properties with changing gas pressures and hydrogen dilution ratios. Finally, we summarized the effects of hydrogen partial pressure on the crystllinity of Si films.In Section Four, we studied the effects of ICP plasma source and growth mechanism ofμc-Si:H thin films in ICP-MS system. First we illustrated the results of characteristics of Si films with changing ICP powers at three different hydrogen dilution ratios. Then we used optical emission spectroscopy (OES) to study the radicals during depositon process of Si films. Finally based on results of sample analysis and OES, we discussed the effects of ICP plasma source and growth mechanism ofμc-Si:H thin films in ICP-MS system.In Section Five, we studied the effects of growth temperature from 150℃to 450℃on the growth of Si films. We showed thatμc-Si:H thin films were also formed by ICP-MS deposition even at growth temperature below 150℃. And we pointed out the precondition for low temperature or even room temperature growth ofμc-Si:H thin films in ICP-MS system.In Section Six, we focused on effects of bias voltage on the growth ofμc-Si:H thin films in ICP-MS system. At first, we demonstrated the oxidation issue of Si thin films deposited by magnetron sputtering. Then we illustrated the effects of negative bias voltages on the growth ofμc-Si:H thin films. And we pointed both the advantage and disadvantage of ion bombardment for the growth of Si films by magnetron sputtering. Finally, we studied the effects of positive bias voltages, and further explained the effects of ion on the growth onμc-Si:H thin films in ICP-MS system.In the conclusion part, we summaried results from Section Two to Section Six and also the unsolved issues need to be studied in the future work.